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Recent Results from STAR Tim Hallman Warsaw University November 28, 2003

Recent Results from STAR Tim Hallman Warsaw University November 28, 2003. PHOBOS. BRAHMS. 12:00 o’clock. BRAHMS. PHOBOS. RHIC. 2:00 o’clock. PHENIX. 10:00 o’clock. STAR. RHIC. PHENIX. 8:00 o’clock. 4:00 o’clock. STAR. 6:00 o’clock. AGS. 9 GeV/u Q = +79. U-line. BAF (NASA).

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Recent Results from STAR Tim Hallman Warsaw University November 28, 2003

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  1. Recent Results from STAR Tim HallmanWarsaw UniversityNovember 28, 2003

  2. PHOBOS BRAHMS 12:00 o’clock BRAHMS PHOBOS RHIC 2:00 o’clock PHENIX 10:00 o’clock STAR RHIC PHENIX 8:00 o’clock 4:00 o’clock STAR 6:00 o’clock AGS 9 GeV/u Q = +79 U-line BAF (NASA) m g-2 LINAC BOOSTER HEP/NP AGS TANDEMS 1 MeV/u Q = +32 TANDEMS Relativistic Heavy Ion Collider (RHIC) • 2 concentric rings of 1740 superconducting magnets • 3.8 km circumference • counter-rotating beams of ions from p to Au • max center-of-mass energy: AuAu 200 GeV, pp 500 GeV RHIC Runs Run I: Au+Au at s = 130 GeV Run II: Au+Au and pp at s = 200 GeV

  3. Time Projection Chamber FTPCs (1 +1) Vertex Position Detectors The STAR Detector Magnet Silicon Vertex Tracker * Coils TPC Endcap & MWPC ZCal ZCal ZCal BBCs Endcap Calorimeter Central Trigger Barrel + TOF patch + TOFr Barrel EM Calorimeter

  4. The STAR Collaboration: 49 Institutions, ~ 500 People U.S. Labs: Argonne, Lawrence Berkeley, and Brookhaven National Labs U.S. Universities: UC Berkeley, UC Davis, UCLA, Caltech, Carnegie Mellon, Creighton, Indiana, Kent State, MIT, MSU, CCNY, Ohio State, Penn State, Purdue, Rice, Texas A&M, UT Austin, Washington, Wayne State, Valparaiso, Yale Brazil: Universidade de Sao Paolo China: IHEP - Beijing, IPP - Wuhan, USTC, Tsinghua, SINR, IMP Lanzhou Croatia: Zagreb University Czech Republic: Nuclear Physics Institute England: University of Birmingham France: Institut de Recherches Subatomiques Strasbourg, SUBATECH - Nantes Germany: Max Planck Institute – Munich University of Frankfurt India: Bhubaneswar, Jammu, IIT-Mumbai, Panjab, Rajasthan, VECC Netherlands: NIKHEF Poland: Warsaw University of Technology Russia: MEPHI – Moscow, LPP/LHE JINR – Dubna, IHEP - Protvino

  5. The Phase Diagram of QCD Early universe quark-gluon plasma critical point ? Tc Temperature colour superconductor hadron gas nucleon gas nuclei CFL r0 Neutron stars vacuum baryon density

  6. schematic view of jet production hadrons leading particle q q hadrons leading particle Vacuum QGP Hard Probes in Heavy-Ion Collisions • New opportunity using Heavy Ions at RHIC Hard Parton Scattering • sNN = 200 GeV at RHIC • 17 GeV at CERN SPS • Jets and mini-jets • High pt leading particles • Azimuthal correlations • Extend into perturbative regime • Calculations reliable • Scattered partons propagate through matter & radiate energy (dE/dx ~ x) in colored medium • Interaction of parton with partonic matter • Suppression of high pt particles “jet quenching” • Suppression of angular correlations

  7. Partonic energy loss in dense matter Thick plasma (Baier et al.): Gluon bremsstrahlung Thin plasma (Gyulassy et al.): • Linear dependence on gluon density glue: • measure DE  gluon density at early hot, dense phase • High gluon density requires deconfined matter • (“indirect” QGP signature !)

  8. hadrons hadrons leading particle What is a jet? Jet: A localized collection of hadrons which come from a fragmenting parton c a Parton distribution Functions Hard-scattering cross-section Fragmentation Function b d High pT (> ~2.0 GeV/c) hadron production in pp collisions:

  9. Parton Distribution Functions Intrinsic kT , Cronin Effect Shadowing, EMC Effect Hard-scattering cross-section c a Partonic Energy Loss b d hadrons Fragmentation Function leading particle suppressed High pT Particle Production in A+A (According to pQCD…)

  10. A key probe, new at RHIC: hard scattering of quarks and gluons Nuclear Modification Factor: Nucleus-nucleus yield <Nbinary>/sinelp+p Another way to test: AA If R = 1 here, nothing “new” going on

  11. Jets in Heavy Ion Collisions at RHIC Jet event in e+e-collision STAR Au+Au collision

  12. z y x Anisotropic Flow py px Elliptic Flow at RHIC Anisotropic (Elliptic) Transverse Flow • The overlap region in peripheral collisions is not symmetric in coordinate space • Almond shaped overlap region • Easier for particles to emerge in the direction of x-z plane • Larger area shines to the side • Spatial anisotropy  Momentum anisotropy • Interactions among constituents generates a pressure gradient which transforms the initial spatial anisotropy into the observed momentum anisotropy • Perform a Fourier decomposition of the momentum space particle distributions in the x-y plane • v2 is the 2nd harmonic Fourier coefficient of the distribution of particles with respect to the reaction plane Peripheral Collisions

  13. Non-central Collisions z y x Anisotropic Flow py px Anisotropic (Elliptic) Flow at RHIC

  14. Statistical Identification of jets in AA Collisions You can see the jets in p-p data at RHIC • Identify jets on a statistical basis in Au-Au • Given a trigger particle with pT > pT (trigger), associate particles with pT > pT (associated) STAR Preliminary Au+Au @ 200 GeV/c 0-5% most central 4 < pT(trig) < 6 GeV/c 2 < pT(assoc.) < pT(trig)

  15. In Detail: High-pT Spectra from STAR Basic Idea: peripheral collisions are p+p like  no suppression central collisions hot and dense matter  suppression

  16. Comparison Au+Au/p+p at RHIC (STAR)

  17. Central/Peripheral Normalized by Nbin suppression suppression

  18. Binary scaling Scaling pp to AA … including the Cronin Effect At SPS energies: • High pt spectra evolves systematically from pp  pA  AA • Hard scattering processes scale with the number of binary collisions • Soft scattering processes scale with the number of participants • The ratio exhibits “Cronin effect” behavior at the SPS • No need to invoke QCD energy loss

  19. Peripheral Au+Au data vs. pp+flow Back-to-back Jet Correlation Results • Ansatz: • A high pTtriggered • Au+Au event is a superposition of a high pT triggered • p+p event plus anisotropic transverse flow • v2 from reaction plane analysis • “A” is fit in • non-jet region • (0.75 < || < 2.24)

  20. Central Au+Au data vs. pp+Flow Back-to-Back Jet Correlation Results

  21. Supression of the Back-to-Back Correlation • Indication of opacity of the source? Trigger: pT>4 GeV/c Correlate: pT>2 GeV/c Away-side correlations disappear as collision becomes more central

  22. Pedestal&flow subtracted A d+Au“control” experiment was been performed! d+Au Run II AuAu results at full energy show strong suppression ! d+Au “control”data needed to distinguish between different interpretations Central AuAu Results show: Observed suppression due to nature of (new) produced matter ! not initial state effects 0 90 180  Degrees

  23. Jet Quenching Result PRL Cover Article Special Colloquium June 17, 2003

  24. Hydro predictions Phys.Rev.Lett. 86, (2001) 402 more central  v2 vs. Centrality • v2 is large • 6% in peripheral collisions • Smaller for central collisions • Hydro calculations are in reasonable agreement with the data • In contrast to lower collision energies where hydro over-predicts anisotropic flow • Anisotropic flow is developed by rescattering • Data suggests early time history • Quenched at later times Anisotropic transverse flow is large at RHIC

  25. Preliminary v2 vs. pT and Particle Mass • The mass dependence is reproduced by hydrodynamic models • Hydro assumes local thermal equilibrium • At early times • Followed by hydrodynamic expansion D. Teaney et al., QM2001 Proc.P. Huovinen et al., nucl-th/0104020 Hydro does a surprisingly good job!

  26. v2 for High pt Particles Phys.Rev.Lett. 90, 032301 (2003) v2 is large … but at pt > 2 GeV/c the data starts to deviate from hydrodynamics

  27. y v2 predictions at high pT pQCD inelastic energy loss + parameterized hydro component distance of fast parton propogation M. Gyulassy, I. Vitev and X.N. Wang PRL 86 (2001) 2537 Jet 2 x Jet 1 • The value of v2 at high pt sensitive to the initial gluon density • Saturation and decrease of v2 as a function of pt at higher pt

  28. ? Elliptic flow as a function of transverse momentum V2(RP) Could this effect be due to Surface emission? V2(2) V2(%) V2(4) STAR Preliminary Significant v2 up to ~7 GeV/c in pt, the region where hard scattering begins to dominate. The data support the conclusion that we have produced a medium that is dense, dissipative, and exhibits strong collective behavior

  29. Λ˚, K°s v2 versus pT: mass dependence or particle type? Results suggest a scaling of v2 versus particle type (meson/baryon) rather than particle mass  flow is built up at the partonic stage (?)

  30.  What we measure? What we expect to see? HBT radii as a function of emission angle 2nd-order oscillations in HBT radii Rside2 reactionplane  Why we're interested?  What should be remembered The size and orientation of the source at freeze-out places tight constraints on expansion/evolution At finite kT, we don't measure the entire source size. We measure "regions of homogeneity" and relating this to the full source size requires a model dependence. HBT Correlations relative to the reactions plane qside qout qlong Heinz, Hummel, Lisa, Wiedemann PRC 044903 (2002)

  31. fp = 90° Rside (small) Rside (large) fp = 0° Centrality Dependence of HBT for AuAu at 200 GeV • 15° bins, 72 CF's total for 12  bins × 3 centrality bins ; × 2 pion signs • 0.15 < kT < 0.65 • Oscillations exist in transverse radii for all bins Results show oscillations which indicate out-of-plane extended source and short lifetime! STAR Preliminary

  32. STAR 130 GeV PHENIX 130 GeV Probing Thermalization: The HBT Puzzle HBT radii pose serious difficulties for hydro models Hydro + RQMD STAR PRL 87, 082301 (2001) PHENIX PRL 88 192302 (2002) “Blast wave” parameterization (Sollfrank model) can approximately describe data (spectra + HBT) …but emission duration must be small  = 0.6 (radial flow), T = 110 MeV R = 13.5  1fm (hard-sphere) emission= 1.5  1fm/c (Gaussian)

  33. In-plane/out-of-plane back-to-back jet suppression STAR preliminary STAR preliminary Back-to-back suppression is larger in the out-of-plane direction

  34. Results on “Soft” Physics • Particle production per participant is large • Total Nch ~ 5000 (Au+Au s = 200 GeV)  ~ 20 in p+p • Nch/Nparticipant-pair ~ 4 (central region)  ~2.5 in p+p •  A+A is not a simple superposition of p+p • Energy density is high ~ 4-5 GeV/fm3 (model dependent) • System exhibits collective behavior (flow) •  strong internal pressure • The system appears to freezes-out very fast • explosive expansion • Large system: at freeze-out  2  size of nuclei

  35. Conclusions About Matter Produced at RHIC: We have produced matter which exhibits features qualitatively different than has been observed before ! • The evolution is fast • Transverse expansion with an average velocity of 0.55 c • Large amounts of anisotropic flow (v2) suggest hydrodynamic expansion and high pressure at early times in the collision history • The duration of hadronic particle emission appears to be very short • The produced matter appears to be opaque • Saturation of v2 at high pT • Suppression of high pT particle yields relative to p-p • Suppression of the away side jet • Statistical models describe the final state well • Excellent fits to particle ratio data with equilibrium thermal models • Excellent fits to flow data with hydrodynamic models that assume equilibrated systems • Chemical freeze-out at about 175 MeV; thermal freeze-out at 100 MeV

  36. Conclusions About Matter at RHIC: Is there a phase with bulk properties which are Partonic ? • The data on high pt suppression and correlations support the conclusion that we have produced a medium that: • is dense; (pQCD theory  many times cold nuclear matter density) • is dissipative( very strongly interacting) • We need to show that: • dissipation and collective behavior occur at the partonic stage • the system is deconfined and thermalized • a transition occurs: can we turn the effects off ? • We need: • extended AuAu run needed to address several important probes that need large data sets ( e.g., pT dependence of suppression; J/, , open charm, heavy baryon / meson flow); also, species and energy scans to map the evolution of key observables. • more guidance from theory (!) particularly on what to expect from hadronic scenarios

  37. Pythia p-p 200 GeV Au-Au Thermal* D+/ D0 0.33 0.455 Ds+/ D0 0.20 0.393 Lc+/ D0 0.14 0.173 J/Y/D0 0.0003 0.013 Pressing the search with heavy flavor: first direct observation at RHIC of open charm in d+Au and min-bias Au+Au collisions Open charm: a probe of initial conditions, and possible equilibration at early times D± K, d+Au D0 K, d+Au A.Andronic, P.Braun-Munzinger, K.Redlich, J.Stachel (nucl-th/0209035) Star Preliminary STAR Preliminary | y |< 0.25, 7 <pt <10 GeV/c |y| < 1, pt < 4 GeV/c Do c quarks thermalize?If yes, ratio of charm hadrons yield changes from p-p to Au-Au ; Ds+ most sensitive. D± K, Au+Au STAR Preliminary

  38. d+Au  p0+X, sNN = 200 GeV East of STAR North South Top To STAR Bottom The STAR Forward Pion Detector • 10 < Ep < 80 GeV • hp ~ 4 (relative to d) BNL, Penn State, IHEP-Protvino, UC Berkeley/SSL, UCLA, ANL • Run 3 Objectives: • Probe of Color Glass Condensate in d+Au •  pT dependence of large h yield • Improve understanding of dynamical origin of AN • in p+p  p0 +X  • Collins effect  sensitivity to transversity • Sivers effect  sensitivity to orbital motion • twist-3 effect  quark/gluon correlations • Serve as local polarimeter at STAR IR

  39. STAR-Spin Results from Run 2 p + p  p0 + X , s = 200 GeV DIS2003 • Measured cross sections consistent with pQCD calculations • Large spin effects observed for s = 200 GeV pp collisions • Status: final analysis complete / paper in final preparation

  40. T Interaction Vertex L R * B STAR spin rotator: OFF  Pvert ON  Plong BBC East 3.3<|h|< 5.0 BBC West Mistuned rotators STAR Spin Rotator Magnet Tuning (Run III result) RHIC polarimeter (CNI) establishes polarization magnitude; Local polarimeter (BBC)establishes polarization direction at STAR. Partial Snake Operation • Use inner tiles of BBC as a Local • Polarimeter monitoring pp collisions. • Rotators OFF  BBC L/R spin asymmetries • comparable to RHIC polarimeter (CNI). • Rotators ON  adjust rotator currents to • minimize BBC L/R and T/B spin • asymmetries. “Double-blind” intentional mis-tune check

  41. Projections for Sensitivity to DG for Run III and Run IV Longitudinal spin asymmetry (ALL) for mid-rapidity jet production  may be first measurements directly sensitive to gluon polarization. Simulation based on Pythia + trigger and jet reconstruction efficiency EMC Barrel Coverage includes 0 < Φ < 2π and 0 < η < 1 Jet Trigger: ET > 5 GeV over one patch (Δη = 1) X (ΔΦ = 1) Jet reconstruction: cone algorithm (seed = 1 GeV, R = 0.7) Polarization 0.4, Luminosity: 3 pb-1

  42. Future STAR Spin Physics Goals G (x) determination via ALL in p + p   + jet + X   – –   u , d determination via ALPV in p + p  W ± + X @  s = 500 GeV At design luminosity, a 10-week runs (with  50% RHICSTAR efficiency) apiece would yield: •  s = 200 GeV, P = 0.7, L = 8  10 31  P 4L eff dt  60 pb –1 •  s = 500 GeV, P = 0.7, L = 2  10 32  P 4L eff dt  150 pb –1

  43. Recent Results from STAR - Conclusions • The first 3 runs in STAR have been an outstanding success producing a wealth of results and new physics; even so, the most important achievements are still goals. The next 1-2 years will be extremely exciting. • The highest priority scientifically for the coming run is to go as far as possible to determine the properties of the qualitatively new, dissipative medium discovered in central Au+Au collisions at RHIC, and to study how these may change at a lower energy. • The STAR spin program is off to a great start. Continued progress in the near-term is critical. • STAR is now on a path to RHIC II. The strategy is to extend the scientific reach of the detector, maintaining the core capability of STAR to provide nearly complete event characterization over a wide range of central rapidity. Upgrades will be staged in such a way as to allow a vigorous physics program between now and 2010. All signs are positive for the MRPC TOF Barrel project becoming an approved construction project in the next few months as the first step to RHIC II in STAR.

  44. No significant deviation seen from chemical thermal models Probing Chemical Equilibrium: Yield Ratios The STAR Experimental Program Tch(RHIC) 175 ± 7 MeV B(RHIC) 51 ± 6 MeV Lattice: (Karsch QM01) Tch(RHIC) 173 ± 8 MeV, NF = 2 Tch(RHIC) 154 ± 8 MeV, NF = 3 STAR Preliminary 13 Ratios 7 used 6 predicted ( P. Braun-Munzinger et al: hep-ph/105229)

  45. pp Minimum Bias Au+Au 40% to 80% STAR Preliminary STAR Preliminary 1.2 pT 1.4 GeV/c |y|  0.5 0.8 pT 0.9 GeV/c |y|  0.5 *(1520) STAR preliminary p+p at 200 GeV  K*0 Resonance production: a tool for precision studies of the late stages of the collision at RHIC , , *(892), *(1385), *(1520) , D*

  46. The full spectrum of strange particles is available in STAR W  f K0s STAR Preliminary L X- X̅+ K*

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